Gonadal and extra-gonadal actions of FSH glycoforms in aging

该项目的长期目标是研究垂体对卵巢和骨功能的控制机制。 年迈的女性。正常的卵巢功能依赖于卵泡刺激素(FSH)，这是一种脑垂体来源的激素 由α-和β-亚基组成的异二聚体糖蛋白。这两个亚基都用两个N-糖基化。 每个亚基中的连接糖链。这种完全糖基化的形式被命名为FSH24。糖基化作用是一种 主要作用于FSH的分泌、血清半衰期和生物学作用。众所周知，脑下垂体的糖基化 促性腺激素也是发情/月经周期和年龄相关的。中国人的生化和生理研究 有几个物种已经发现了独特的低糖基化变体，只在α中包含糖链，但 β亚基上有一个或没有。这些变体被称为低糖基化的FSH糖形式和 指定为FSH21、FSH18或FSH15。最重要的是，低糖基化的FSH形式与完全糖基化的FSH形式的比率是 发现与年龄相关的，高水平的完全糖基化变异主要存在于围产期/后 更年期妇女并可能导致与衰老相关的骨质流失。然而，在体内截然不同的 这些FSH糖型变体在正常和衰老的卵巢和骨骼中的生物学功能尚不清楚 生理学。中心假设是FSH上的糖基化是一种与年龄相关的改变靶点的开关 从卵巢到骨骼的组织特异性。这一假设将用基因工程小鼠进行验证。 有两个具体目标的模型。在目标1中，我们将测试卵巢发育和功能随着年龄的增长而递增。 利用FSHB基因缺失的小鼠表达单独糖化形式的FSH。这种遗传策略将使我们能够测试 系统地研究各种糖基化FSH变异体在小鼠卵巢生理中的体内生物学作用 缺乏内源性小鼠促卵泡激素。在目标2中，首先，我们将使用表达FSH糖形的小鼠并测试 骨骼发育随着年龄的增长而变化。明确地测试FSH对骨骼的直接作用，在一个 方法，我们将设计FSHR在破骨细胞中通过Cre-lox基因选择性缺失的小鼠 接近。在第二种方法中，我们将开发一种基因工程小鼠品系，使其能够 FSH在所需时间的暂时性丢失。对这些转基因小鼠模型的功能分析将 通过外推确定体内FSH变异体在卵巢衰老过程中的不同生物学作用 卵巢衰老。这些新颖的小鼠模型还将使我们能够直接测试衰老是否与 骨丢失依赖于FSH配体或FSH受体介导的破骨细胞信号转导。我们的 研究可能会揭示一种新的现象，即脑垂体糖蛋白上的年龄依赖性N-糖基化转换 导致靶组织特异性(卵巢与骨骼)改变的激素，并可能导致 干预老年妇女骨丢失的新治疗选择。

The long-term goal of this project is to study mechanisms of pituitary control of ovarian and bone function in aging women. Normal ovarian function is dependent on follicle-stimulating hormone (FSH), a pituitary derived heterodimeric glycoprotein consisting of a α-and a β-subunit. Both the subunits are glycosylated with two N- linked sugar chains in each subunit. This fully glycosylated form is designated FSH24. Glycosylation plays a major role in secretion, serum half-life and biological actions of FSH. It is known that glycosylation of pituitary gonadotropins is also estrous/menstrual cycle- and age-specific. Biochemical and physiological studies in several species have identified unique hypo-glycosylated variants consisting of sugar chains only in the α but either one or none on the β subunit. These variants are known as hypo-glycosylated FSH glycoforms and designated as FSH21, FSH18 or FSH15. Most importantly, the ratio of hypo- to fully-glycosylated FSH forms is found age-dependent, with high levels of fully-glycosylated variant predominantly present in peri/post- menopausal women and may contribute to the aging-associated bone loss. However, the distinct in vivo biological functions of these FSH glycoform variants are unknown in normal and aging ovarian and bone physiology. The central hypothesis is that glycosylation on FSH is an age-related switch that changes target tissue specificity from ovary to bone. This hypothesis will be tested using genetically engineered mouse models in two specific Aims. In Aim 1, we will test ovarian development and function progressively with aging using Fshb null mice expressing individual glycosylated forms of FSH. This genetic strategy will allow us to test systematically the in vivo biological actions of each glycosylated FSH variant in ovarian physiology in the absence of endogenous mouse FSH. In Aim 2, first, we will use the FSH glycoform-expressing mice and test bone development as a function of aging. To unequivocally test the direct actions of FSH on bone, in one approach, we will engineer mice in which Fshr will be selectively deleted in osteoclasts by a Cre-lox genetic approach. In a second approach, we will develop a genetically engineered mouse line that permits creating temporal loss of FSH at desired times. Functional analyses with these genetically altered mouse models will identify distinct biological actions of FSH variants in vivo during ovarian aging and by extrapolation, in human ovarian senescence. These novel mouse models will also allow us to directly test whether aging-associated bone loss is dependent on FSH ligand or FSH receptor-mediated signaling in osteoclasts in the bone. Our studies may unravel a novel phenomenon of age-dependent N-glycosylation switch on a pituitary glycoprotein hormone that results in alterations in target tissue specificity (ovary versus bone) and may potentially lead to new therapeutic options for intervention of bone loss in aging women.